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Professional studies tell you whether N95 masks can be reused after disinfection? Which method of disinfection is best?

Time : 2020-05-18 Hits : 6

Aerosol transmission is one of the means of transmission by novel coronavirus. When a patient coughs, sneezes, or even talks or breathes, they spread virus-carrying micron-sized aerosols into the air. Many small aerosols remain in the air for a long time, putting people at risk of infection. Therefore, wearing a mask has become one of the effective measures to prevent and control novel coronavirus transmission.


The filtration efficiency of N95 respirator on 0.3 feet diameter sodium chloride aerosol is more than 95%, which can block the spread of the virus. Medical protective grade N95 masks have been in short supply worldwide since the outbreak. In this case, the reuse of masks after disinfection has important practical significance. Stanford university and 4C Air recently evaluated different disinfection methods for melt-blown nonwovens, the core filtration material for N95 masks.


N95 mask melt blown nonwoven fabric structure and filtration diagram

The researchers chose the high temperature (75 ℃, 30 min), water vapor (about 15 cm above in boiling water, 10 min), 75% ethanol solution soaked, and household disinfectant spray (containing 2% sodium hypochlorite) (0.3 ~ 0.5 mL) and five kinds of commonly used disinfection measures such as ultraviolet irradiation of melt-blown nonwovens disposable disinfects processing, and then test its performance change. The results showed that the filtration performance of melt-blown nonwovens decreased significantly after ethanol immersion and household disinfectant treatment, while other disinfection methods had no effect on the filtration efficiency of melt-blown nonwovens.


Effects of heating, steam and ultraviolet light on the filtration properties of melt-blown nonwovens

The researchers also studied the effects of multiple sterilization procedures on the filtration properties of melt-blown nonwovens, which they cycled through using high temperatures, water vapor, and ultraviolet radiation. The results showed that the filtration efficiency of melt-blown nonwovens decreased sharply after 5 times of water vapor cycle treatment, while the filtration performance of melt-blown nonwovens remained unchanged after 10 times of high temperature and ultraviolet lamp irradiation.


The effect of ultraviolet light on the properties of melt-blown nonwovens

The effects of humidity and temperature on the filtration properties of melt-blown nonwovens were further studied. The results showed that at 85°C, after 20 times of treatment in different humidity, the filtration performance of melt-blown nonwovens did not significantly decrease, and its structure did not change significantly. Even after 50 times of treatment at 85°C and 30% humidity, the filtration performance of melt-blown nonwovens only slightly decreased. At the same time, the same treatment was applied to the N95 mask, and its filtration performance did not decrease significantly. However, there is an upper limit of 125℃ for the temperature of heating treatment, which may be because the temperature is close to the melting point of the material at this time, and the change of its microstructure will lead to the decrease of electrostatic electrots.


The change of filtration performance after heating the melt spraying cloth and mask at different temperature and humidity

Based on the above conclusions, it is recommended to avoid the use of alcohol, disinfectant, soap and water to clean and disinfect N95 masks in the process of reuse. Ultraviolet disinfection and high-temperature disinfection are optional disinfection methods. However, due to the low penetration of ultraviolet radiation and limited bactericidal capacity, high-temperature treatment below 100°C has little impact on melt-blown nonwovens and can be reused for many times. Therefore, high-temperature treatment below 100°C is the best disinfection method for N95 masks.

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